A man who died after jumping into the River Liffey last Saturday was attempting to get away from an attacker who had stabbed him, gardaí believe.The man has been named as Thomas Griffin, a 31-year-from Ballyfermot in Dublin. Gardaí investigating the attack on Griffin on Saturday night sealed off an area around War Memorial Gardens in Islandbridge and on the Chapelizod Road as part of the inquiry into his death.He was a brother of James Griffin, who was stabbed to death aged 26 at an illegal rave in Dublin in 2014. James Griffin’s killing remains unsolved.James Griffin, brother of Thomas Griffin, was murdered in 2014. His attackers have never been brought to justice. Gardaí believed there were a number of assaults and public order incidents in that area on Saturday night and that Griffin sustained a number of wounds in a knife attack.Though he had been slashed and was badly injured, he jumped into the Liffey in an effort to get to safety and managed to swim the width of the river.Cllr Daithí Doolan, Sinn Féin’s group leader on Dublin City Council and councillor for the Ballyfermot-Drimnagh area, extended his sympathies to Griffin’s family and friends.“His death was tragic, made worse by the questions that surround his untimely death,” he said, appealing to witnesses, or anybody with information, to contact gardaí and aid their investigation.“It is hugely important that the family find out what happened to Thomas. His family and friends deserve to know what happened to their loved one.”Garda headquarters said its personnel were part of the emergency services response “following reports that a male had swam across the River Liffey to lands adjacent to Chapelizod Road, following an alleged incident of assault in the vicinity of the War Memorial Gardens” at about 10.20pm on Saturday.“The male, aged in his 30s, was treated at the scene by personnel from the Dublin Fire Brigade before being removed by ambulance to St James’s Hospital, where he subsequently passed away on Sunday.”Investigating gardaí at Clondalkin Garda station were awaiting the results of a postmortem examination, which would determine the nature of the inquiry, including whether Griffin’s knife injuries were the direct cause of his death.An investigation team, under a senior investigating officer, has been established at Clondalkin station and they are appealing for witnesses to come forward.Gardaí are looking to speak to anyone who was in the area at the time, including motorists recording dashcam footage, between 9pm and 10.45pm on Saturday. They also believe other people who were in the area at the time, and were perhaps known to Griffin, have vital information about why he was attacked and by whom.James Griffin, who died after being stabbed in the neck in west Dublin almost 12 years ago, was attacked at an illegal rave in a disused unit at Park West Business Park in November 2014. He had sustained 10 wounds to the neck, torso and arm before his attackers, who were never caught, fled the scene in a taxi.